Field of the Invention
The invention relates to an injector for mixing two propellants upstream from a combustion chamber, for example the combustion chamber of a rocket motor. An injector refers to an assembly made up of one or more injection elements and a structure forming a support and including means for supplying propellants for the concerned injection element(s).
Description of the Related Art
U.S. Pat. No. 6,502,385 describes an injector of the aforementioned type, i.e., including at least one injection element mounted between two fixed plates spaced apart from each other. The assembly making up the injector is also called “injection head”. The or each injection element is rigidly secured to the two plates and assembled thereto. According to the embodiment specifically described in this prior art, the injection element is screwed to an upstream base plate and riveted to a downstream plate topping the combustion chamber. The injection element is of the tricoaxial type, i.e., comprising an annular middle coaxial duct for a first propellant and two coaxial ducts for a second propellant, an annular internal coaxial duct and external coaxial duct, respectively. The downstream ends of these three ducts open beyond a hole of the downstream plate such that the mixture of the two propellants is discharged, toward the combustion chamber. The outer tubular enclosure, delimiting the external coaxial duct, is riveted to the downstream plate. The injection element(s) contribute to stabilizing the position thereof relative to the upstream plate and preventing it from deforming.
Furthermore, the described injection element is such that the internal coaxial duct and the external coaxial duct (in which said second propellant circulates) communicate by passages formed radially and pass through the middle coaxial duct where the first propellant circulates. It is therefore difficult to calibrate the respective flow rates of said second propellant in the internal and external coaxial ducts. Furthermore, the interlocking of the parts making up the injection element, due to the existence of these passages through the middle coaxial duct, is fairly complex and requires implementing delicate and expensive assembly techniques.